The present invention relates to a lubricating oil for metal working and more particularly to a lubricating oil effectively usable in rolling, which is excellent in anti-heat scratching properties and also which can reduce rolling load and improve gloss of the rolled plates.
Metal working oils such as a rolling oil, a pressing oil, an extrusion oil, a drawing oil, a punching oil and a cutting oil are required to be excellent in the necessary properties. For rolling oils, in particular, it is required that (1) they are excellent in rolling properties; in other words, they can produce a high reduction in pressure at a low rolling load, (2) they cause no heat scratching under severe conditions, (3) they permit the production of rolled plates having good gloss, and so forth.
In order to obtain a rolling oil satisfying the above requirements, attempts to compound various diester compounds to the base oil have been made. U.S. Pat. No. 3,396,111, for example, discloses the diesters of unsaturated dibasic acids having a small carbon atom number, such as dilauryl maleate, and higher fatty acids.
Rolling oils containing the above diester compounds are satisfactory to a certain extent in respect of (1) and (2) above, but not in respect of (3). In fact, a rolling oil sufficiently satisfactory in all the above requirements (1) to (3) has not yet been obtained.